The present invention relates in general to the delivery of stents into a body lumen, such as a blood vessel, to maintain the patency thereof. More particularly, the present invention relates to endcaps that are used in conjunction with the delivery of stents within a body lumen.
In a medical procedure known as percutaneous transluminal coronary angioplasty (PTCA), a balloon catheter is used to dilate the lumen of a coronary artery which has become narrowed or restricted due to the accumulation of atherosclerotic plaque along the artery wall. In the PTCA procedure, a balloon catheter is advanced through the vasculature to the stenosis and the balloon is inflated to radially compress the atherosclerotic plaque against the inside of the artery wall. The balloon is then deflated so that the dilation catheter can be removed and blood flow resumed through the dilated artery.
Occasionally, the inflation of the balloon within the artery lumen will dissect either the stenotic plaque or the intima of the blood vessel or both. Subsequent to the balloon being deflated and removed, blood can flow between the arterial wall and the dissected lining thereby constricting the flow passage or causing a section of the dissected lining, commonly called an xe2x80x9cintimal flap,xe2x80x9d to be forced into the flow passageway. In the event of partial or total occlusion of an artery by a dissected arterial lining, the patient is put in an extremely dangerous situation requiring immediate medical attention.
Another problem that frequently arises after an angioplasty procedure is the appearance of a restenosis at or near the site of the treated artery. The restenosis may appear due to the accumulation of additional atherosclerotic plaque but is typically due to neointimal proliferation as a result of vessel injury and foreign body response. When restenosis appears, the treated patient may require an additional angioplasty procedure or other treatment such as by-pass surgery, if an additional angioplasty procedure is not warranted.
Due to the problems caused by dissections of the arterial lining or the appearance of restenosis, much research has been performed on ways to maintain the patency of an artery after the angioplasty procedure is completed. In recent years, expandable endoprosthetic devices, commonly called xe2x80x9cstents,xe2x80x9d have gained widespread acceptance as a means to support the arterial walls and maintain the patency of a treated vessel. Stents are generally cylindrically shaped intravascular devices that are placed within a damaged artery to hold it open and maintain unimpeded blood flow. Stents prevent dissected arterial linings from occluding an artery by pressing the dissected tissue against the arterial wall until natural healing results in the re-securing of the dissected tissue to the arterial wall. Compared to balloon angioplasty, stents improve short term outcome by preventing elastic recoil and long term outcome by a reduction in positive vessel remodeling.
As with all interventional techniques, the use of stents requires particular training and technique for optimum placement in the coronary vasculature. There are many measures of the performance of a stent delivery system that affect its ease of use and clinical utility. Low profile, flexibility and good push characteristics affect the ability of the stent to cross the lesion. It is critical that the stent stay on the delivery system until it is at the desired site. During placement, stents experience frictional forces as they negotiate tortuous vasculature. Furthermore, stents often have to cross calcified lesions and already deployed stents where there is the chance of catching a strut. Sometimes the stent cannot be deployed for a variety of reasons. In these instances, the stent must be able to be pulled back into the guiding catheter without being stripped off the balloon. Despite care in the handling of stents currently, stents do become dislodged from the delivery systems or damaged and require removal. The consequences of losing a stent can be life threatening and can require immediate surgery.
What has been needed and heretofore unavailable is a device that provides a means for preventing longitudinal movement of the stent off of the balloon. The device should additionally make it more difficult for the stent edges to catch on other objects as the stent is moved within the vasculature. Additionally, the device should exhibit a relatively low profile for delivery through the vasculature. The present invention satisfies these needs and others.
As used herein, the terms xe2x80x9cproximal,xe2x80x9d xe2x80x9cproximallyxe2x80x9d and xe2x80x9cproximal directionxe2x80x9d when used with respect to the invention are intended to mean moving away from or out of the patient, and the terms xe2x80x9cdistal,xe2x80x9d xe2x80x9cdistallyxe2x80x9d and xe2x80x9cdistal directionxe2x80x9d when used with respect to the invention are intended to mean moving toward or into the patient. These definitions will apply with reference to apparatus, such as catheters, guide wires, stents and the like.
The invention provides for a stent deployment system for delivering a stent within a body lumen. The system includes a novel endcap that serves many important functions.
In one aspect of the invention, there is provided an endcap, including a tapered member having a first end and a second end. The first end and the second end each have an aperture therethrough. The tapered member has a pre-expanded condition and an expanded condition. The first end of the tapered member is positioned against an end of a stent mounted on a catheter when the tapered member is in the pre-expanded condition. The first end of the endcap interdigitates or meshes with respect to an end of the stent.
In another aspect of the invention, there is provided a stent deployment system for delivery of a stent within a body lumen. The system includes a catheter for delivering and implanting a stent. The distal end of the catheter includes an expandable member upon which a stent is mounted. An endcap is positioned in apposition with an end of the stent. The endcap is in the shape of a tapered member including a first end and a second end, the first end and the second end each having an aperture therethrough. The tapered member has a pre-expanded condition and an expanded condition. The first end of the tapered member is positioned against an end of the stent when the tapered member is in the pre-expanded condition. The first end of the end cap interdigitates with respect to an end of the stent. The endcap decreases the deflation time of the expandable member and assists in folding of the expandable member upon deflation. The endcap also holds the stent on the expandable member before inflation.
In yet another aspect of the invention, there is provided a stent deployment system for delivery of a stent within a body lumen. The system includes a catheter having an expandable member. A stent is mounted on the expandable member. A means is provided for retaining the stent on the expandable member. The means for retaining interdigitates with the stent and has a pre-expanded condition and an expanded condition. A first end of the means for retaining is positioned against an end of the stent when the means for retaining is in the pre-expanded condition.
In a further aspect of the invention, there is provided a method of forming an endcap. A catheter is provided having a proximal end and a distal end, wherein the distal end has an expandable member and a stent is mounted on the expandable member. A liquid is introduced onto the expandable member distal to the stent. The liquid is allowed to harden such that an interdigitating endcap is formed.
In a still further aspect, there is provided a method of forming an endcap, utilizing a tapered cylindrical mold and a catheter having a proximal end and a distal end. The distal end of the catheter has an expandable member and a stent is mounted on the expandable member. A liquid is introduced into the mold. The liquid is allowed to harden such that an endcap is formed. The endcap is applied to the catheter distal to the stent with an adhesive.